Abstract
Solubility constants of rare earth (RE) nitrates crystalline hydrates are determined in a wide temperature range (−30 to 120°C), salts solubilities and phase diagrams of water–RE nitrate systems are calculated. For multicomponent (n > 5) solutions of RE nitrates the assessment of solution properties as well as phase diagrams are shown to be feasible within experimental uncertainty. In case of mixtures of RE nitrates with similar hydrodynamic radii of ions, the parameters of RE1–RE2 interparticle interaction can be ignored without losing accuracy of thermodynamic modeling.
Highlights
The production and consumption of rare earth (RE) elements in different areas of science and technology are key economic indicators of industrial countries
It has proven its reliability with respect to extraction systems, as it allowed to calculate the binary diagram of the water–tributyl phosphate system, which was unsuccessful with any other models [34]
The expression for the molar excess Gibbs energy in the electrolyte generalized local composition model (eGLCM) model contains three terms: G ex = GLexR + GMexR + GSeRx, where GLexR is the contribution of long-range interactions, GMexR is the contribution of middle-range interactions, and GSeRx is the contribution of short-range interactions
Summary
The production and consumption of rare earth (RE) elements in different areas of science and technology are key economic indicators of industrial countries. High-purity RE elements are of particular interest due to their active use as catalysts in oil refinement, luminescence activators, components of hightemperature superconductors, permanent magnets, laser crystals, etc. The available production capacities are gradually becoming insufficient to satisfy the growing demand for high-purity RE elements. The technology of liquid-phase extraction from acidic water–organic solutions with subsequent deposition of the product from the raffinate or aqueous re-extract is currently mostly used [1]. Thermodynamic modeling can be a reasonable alternative which allows to reduce considerably the time and labor for optimization of the separation process. The aim of this work was to construct a thermodynamic model for describing the properties of phases and their equilibria in multicomponent systems of water and RE nitrates in a wide range of temperatures
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